Occupation and cancer - European Trade Union Institute (ETUI)

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770 E. Pukkala et al.
in the same main occupational category in 1975 and
1980. The percentage among men varied from 91%
in transport to 82% in administration and manufacture,
and among women from 89% in communication
to 77% in administration. The comparison
between 1980 and 1985 also indicated a very stable
labour market in Finland at that time [153]. In
Denmark, a comparison of subsequent birth cohorts
in one census indicate that at least one fourth of men
working in manufacture, construction and transport
in 1970 had a background in agriculture [156]. A
background in agriculture is expected to affect the
cancer pattern of such occupational categories, as
the cancer risk of farmers is in general low and as
farmers normally had lower tobacco consumption
than other occupational categories.
Even for those who remained in the same
occupation, job conditions may have changed considerably.
Although in some occupations where the
physical demands are still high, for instance mining,
forestry, fishing, agriculture, construction, cleaning
and some health care work, the physical work load
has generally diminished with the automatisation of
industrial processes. Physical activity during leisure
time has to be considered in addition to physical
activity at work when it comes to interpreting the
occupational differences in, e.g., the incidence of
breast and colon cancers.
In Finland, occupation specific SMRs were calculated
in two ways: first based on one single census
(1980) and then restricted to persons who had
stayed in the same occupation in subsequent censuses.
The SMR estimates were practically identical
[157]. We believe that the present results based on
occupation in one census give, in most instances,
similar results that we would have gotten from
categorisations based on occupational titles kept in
several censuses. This phenomenon will be studied
in detail in specific NOCCA studies in restricted
data sets for which we have data on several censuses
available.
Validity of cancer incidence data
Nordic countries are well known of their long
tradition of high-quality population-based cancer
registration [158]. In Denmark, several independent
studies indicate a good coverage of the cancer
registration from the very beginning in 1943. Comparison
between 1977 data from the newly established
hospital discharge register and the cancer
register showed that 95% of the cancer cases in the
hospital discharge register were also known in the
cancer register, with the deficits seen for cancers of
the digestive organs, breast, female genital organs
and lymphatic and haematopoietic tissue [159]. In
1997, the registration of cancer in Denmark was
moved from the Danish Cancer Society to the
National Board of Health to be part of other national
registration activities and based on electronic data
capture. The change caused severe delays both in the
cancer registration process and the mortality reporting,
and in May 2008 the newest statistics were from
2003. The effects of the system change on the
coverage and accuracy are not yet known.
Cancer registration in Norway has been compulsory
from 1953, and was from the beginning based
on a combination of reporting from clinical and
pathology departments [160]. A comparative study
was undertaken for two counties in 1976 between
the cancer register data and data retrieved from the
Economic and Medical Information System. The
study showed an overall completeness of the cancer
register of 98%, with the deficit coming in particular
from leukaemia and multiple myeloma [192]. For all
cancers registered since 1953, 86.5% are histologically
verified, and 1.3% of the diagnoses are based
on death certificates alone [161].
Cancer registration in Finland is, like in Norway,
based on a combination of reporting from clinical
and pathological departments, and the registration
has been compulsory since 1961. A linkage was
made between the data from the cancer register and
from the national hospital discharge register for
1985 1988. The agreement was good (about 99%)
for most diagnostic groups, but showed about a 10%
underreporting in the cancer register for benign
neoplasms of the central nervous system, mainly
among elderly people, chronic lymphatic leukaemia
and multiple myeloma [162]. The main problem
was slowness of reporting of these diseases; most
of them were later reported via the normal registration
procedure. The same phenomenon has been
reported from other Nordic countries, e.g. Denmark
[163] and Iceland [164].
The Icelandic Cancer Registry, which was
founded in 1954, receives electronic notifications
from the pathology and haematology laboratories on
all cancers and other reportable neoplasms in the
country that are diagnosed at those laboratories.
This information is supplemented by reports from
hospital departments, healthcare facilities, privatepracticing
consultants and information on death
certificates. Recent results from record linkage with
the Hospital Discharge Registry indicate 99% completeness
of the registry [164].
The registration procedure in Sweden has been
somewhat different, as death certificates have not
been used as a data source. Validation studies have
been made by linking the cause of death registry with
the cancer registry [165,166]. The studies showed a
drop out in completeness of a maximum of 4.5%,